There are known a piezoelectric actuator which utilizes deformation of a piezoelectric element and a piezo type ink jet head which applies pressure to ink by a piezoelectric actuator to discharge ink drops (for example P Patent Literature 1 and 2).
For example, the piezoelectric actuator of an ink jet head in Patent Literature 1 has a base in which a plurality of concave pressurizing chambers in which ink is filled are formed and a piezoelectric element which is superimposed on and fastened to the base so as to close the pressurizing chambers. The piezoelectric element in Patent Literature 1 is a so-called unimorph type and has, from the base side, a diaphragm, common electrode, piezoelectric body, and individual electrodes in that order. The piezoelectric body is polarized in a thickness direction (lamination direction). When voltage is applied to the piezoelectric body by the common electrode and individual electrodes, the piezoelectric body contracts in the surface direction and that contraction is limited by the diaphragm. As a result, the piezoelectric element is bent to the pressurizing chamber side (center side displaces to the pressurizing chamber side), so pressure is given to the ink in the pressurizing chamber.